Ab initio calculations are carried out to study linear NCH•••(NCX)1–5 and NCLi…(NCX)1–5 clusters (X=F, Cl, Br). The aim is to study the influence of halogen-bonding cooperativity on the strength and bonding properties of hydrogen or lithium bond. Particular attention is given to parameters such as binding distances, interaction energies and cooperative energies in these systems. According to our results, the halogen-bonding cooperativity between the NCX molecules has an enhancing effect on the strength of hydrogen and lithium bonds, with an increase of 0.33-0.93 and 0.19-0.43 kcal/mol in NCH•••(NCX)n and NCLi•••(NCX)n, respectively. The enhancing effect of halogen bond on the hydrogen and lithium bond is dependent on the nature of halogen atom, and increases as X= F < Cl < Br. The enhancing mechanism is analyzed with the parameters derived from the topological analysis of the electron density and orbital interaction.
